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Fire Load Calculation Calculator

Work out fire load calculation instantly with clear inputs, formula shown and shareable results.

About Fire Load Calculation Calculator

Fire load density is the effective heat content of the combustibles divided by compartment floor area, with a combustion efficiency factor because not all material burns completely. Dividing by about 20 MJ/m² per minute of standard fire exposure gives an equivalent fire duration, which is what fire resistance periods are calibrated against.

Formulas

Fire load density

MJ/m² = mass x calorific value x combustion efficiency / floor area

Equivalent duration

Minutes = fire load density / 20

Worked example

With the default values below, Fire Load Calculation Calculator returns Fire load density of 192.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Mass of combustible materialminimum 0 kg
3,000 kg
Average calorific valueminimum 0.1 MJ/kg
16 MJ/kg
Compartment floor areaminimum 0.1 m²
200 m²
Combustion efficiencyaccepts 10–100 %
80 %

Results

Fire load density
192.0 MJ/m²
Total fire load
38,400 MJ
Equivalent fire duration
9.6 min
Hazard category
Low fire load

Step by step

  1. 1Values used
  2. 2Fire load density
  3. 3Equivalent duration
  4. 4Fire load density= 192.0 MJ/m²
  5. 5Total fire load= 38,400 MJ
  6. 6Equivalent fire duration= 9.6 min
  7. 7Hazard category= Low fire load

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Preliminary estimate only. Fire load assessment and required fire resistance must be determined by a qualified fire engineer to the applicable code.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Fire load assessment and required fire resistance must be determined by a qualified fire engineer to the applicable code.

Frequently Asked Questions

How is the Fire Load Calculation figure worked out?

MJ/m² = mass x calorific value x combustion efficiency / floor area. Fire load density is the effective heat content of the combustibles divided by compartment floor area, with a combustion efficiency factor because not all material burns completely.

Does ventilation affect the outcome?

Strongly. The same fire load burns slowly in a poorly ventilated compartment and fiercely in a well ventilated one, which is why modern fire engineering uses ventilation-controlled parametric curves rather than fire load alone.

What values do I need to enter?

This calculator takes 4 inputs: Mass of combustible material, Average calorific value, Compartment floor area, Combustion efficiency. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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